Messages in this thread | | | Date | Fri, 1 Jun 2007 13:19:50 -0700 | From | Paul Jackson <> | Subject | Re: [RFC] [PATCH] cpuset operations causes Badness at mm/slab.c:777 warning |
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> There are no checks necessary. Your function worked fine so far for > the case of zero objects with the pointer returned by kmalloc. If the > code is correct then it will not dereference the pointer to the zero > sized array. If not then we may find a bug and fix it.
I suspect you got lucky. The check for a full pidarray[] in the routine pid_array_load() occurs -after- a pid is put in the array. If a task showed up in this cpuset at the wrong time, we would fall over and die in the code:
static int pid_array_load(pid_t *pidarray, int npids, struct cpuset *cs) { int n = 0; struct task_struct *g, *p;
read_lock(&tasklist_lock);
do_each_thread(g, p) { if (p->cpuset == cs) { pidarray[n++] = p->pid; /* Death if pidarray == NULL */ if (unlikely(n == npids)) goto array_full; }
} while_each_thread(g, p);
Perhaps if you moved the "if (unlikely(n == npids))" test before the "pidarray[n++] = p->pid" assignment, it would be safe.
And does the next line of code, the call to sort() after the call of pid_array_load(), work with pidarray == NULL and npids == 0:
npids = pid_array_load(pidarray, npids, cs); sort(pidarray, npids, sizeof(pid_t), cmppid, NULL); /* <== ?? */
Off hand, I didn't know. I guess it must, or you would have already tripped over it.
-- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson <pj@sgi.com> 1.925.600.0401 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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